Many wouldn’t be seen dead in them—even with the incentives provided by rising inflation and the fallout from the collapse of the sub-prime loans market in the United States. Not even the “think of a number then double it” methods favoured by gas and electricity suppliers in raising their prices have persuaded diehards that it’s worth changing the habits of a lifetime by shopping at discount supermarkets.

For other people, though, outlets such as Aldi, Lidl, and Netto are an increasingly important lifeline. They are typified by their …